"Space Battleship Great Yamato" is a science fiction manga series set in a future where Earth faces existential threats from alien forces. The story begins in the year 2199, as Earth is under relentless attack by the Gamilas, an alien race bombarding the planet with radioactive meteorites, rendering the surface uninhabitable. Humanity has retreated underground, but resources are dwindling, and time is running out. The Earth Defense Force devises a desperate plan to save the planet by retrofitting the ancient battleship Yamato into a state-of-the-art spacecraft capable of interstellar travel.

The Yamato is tasked with a critical mission: to travel to the distant planet Iscandar, located in the Large Magellanic Cloud, to retrieve a device called the Cosmo Cleaner D, which can cleanse Earth's radiation and restore its environment. The journey is perilous, as the crew must navigate through hostile space, evade Gamilas forces, and overcome numerous obstacles. The crew, led by Captain Juzo Okita, includes key figures such as Susumu Kodai, a young and determined officer; Yuki Mori, a skilled analyst and Kodai's love interest; and Daisuke Shima, the ship's chief navigator. Each character brings unique skills and perspectives, contributing to the Yamato's survival and success.

As the Yamato ventures deeper into space, the crew encounters various alien species, uncovers secrets about the Gamilas and Iscandar, and grapples with moral dilemmas. The Gamilas, initially portrayed as ruthless invaders, are revealed to have their own struggles and motivations, adding complexity to the conflict. The series explores themes of sacrifice, resilience, and the cost of war, as the crew faces personal losses and challenges their own humanity in the face of overwhelming odds.

The narrative builds toward a climactic confrontation with the Gamilas, culminating in a battle that tests the limits of the Yamato and its crew. The resolution of the mission to Iscandar brings both hope and tragedy, as the crew must make difficult choices to secure Earth's future. The series balances action-packed space battles with introspective moments, creating a compelling and multifaceted story that has resonated with audiences since its debut.